1. Field of the Invention
This invention relates to a transmission system for an image display device, and electronic equipment. In more detail, it relates to a transmission system for an image display device, which transmits a signal between an image display driver IC and an image processing IC, and electronic equipment using the same.
2. Description of the Related Art
Electronic equipment using a conventional transmission system for an image display device will be described below in connection with a liquid crystal display device, which is one of the most common image display devices.
An active matrix type liquid crystal display device has an image display part in which a plurality of pixels are arrayed in a matrix shape. This image display part has two boards and a liquid crystal sealed between the boards. In order to generate an electric field in the liquid crystal at the pixels, pixel electrodes corresponding to the respective pixels are formed on one board, and counter electrodes are formed on the other board so that each counter electrode faces an associated pixel electrode.
In the above liquid crystal display device, the board having the pixel electrodes are provided with a plurality of scanning signal lines and data signal lines for driving the pixels such that they intersect each other. The intersecting portions are each formed with a liquid crystal driving device formed of a thin film transistor (TFT) having a switching function of the pixel electrode.
In the pixels of the liquid crystal display device, an image is formed based on an image signal inputted from an image processing IC (Integrated Circuit). Scanning signals applied to the scanning signal lines and data signals applied to the data signal lines are generated from the image signal. Liquid crystals of the respective pixels are controlled by the ON/OFF control of the transistors by the scanning lines and the data signals, whereby the image is displayed on the image display part.
The liquid crystal display device is provided with a scanning driver IC for driving the scanning signal lines, and a data driver IC for driving the data signal lines. These driver ICs are referred to as image display driver ICs. As a method for connecting an image display driver IC to a liquid crystal display part, the TAB (Tape Automated Bonding) method and the COG (Chip On Glass) method are known (for example, JP2008-241748 A (Patent Document 1)).
In the TAB method, a TCP (Tape Carrier Package) is used in which, for example, as shown in FIG. 24, a data driver IC 102 is bonded to a flexible printed-wiring board (flexble PWB) 101. The TCP is electrically connected to a connection portion provided at a periphery of a glass board 105 formed with a liquid crystal display part 104 by an ACF (Anisotropic Conductive Film). A scanning driver IC 103 is also electrically connected in the same manner.
In the COG method, as shown in FIG. 25, a data driver IC 102 is directly mounted on a glass board 105 at a periphery thereof. The data driver IC 102 is electrically connected to data signal lines by the ACF. A scanning driver IC 103 is also electrically connected to scanning signal lines in the same manner. In FIG. 25, the same component parts as those shown in FIG. 24 are designated by the same reference numerals.
Recently, in the field of image display devices, development of multicolor and high resolution has been advanced, signals transmitted between the image processing IC and the image display driver IC have a high frequency, and the number of bits of inputted data tends to increase. Therefore, in the flexible PWB in which a high-speed signal is transmitted between the image processing IC and the image display driver IC, and which has a bent structure when it is used, an influence of an impedance mismatch becomes particularly conspicuous, and there are problems that an electromagnetic noise is radiated to other equipment (EMI), and such equipment picks up a noise component (EMS). These become a major problem in realization of high resolution.